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Re: Hybrid pot still/Nixon Stone still design

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  • mattdistiller
    Message 1 of 4 , Jan 29, 2002
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      << 4. Would a gate valve or a ball valve be better for each of the
      two
      > valves (2" and 3/4")? I don't want fine control, basically just
      want
      > on/off. I was thinking ball valves? >>
      >
      > I would say to use the ball valve.>>

      I just went and looked at ball v's gate valves, and while I thought I
      would prefer to use the ball, in a 2" size, gate valves are about
      half the price, and look to be solid metal construction, compared to
      the plastic components in the ball valve. Does anyone know anything
      about the comparability of the seal maintained by both?

      << If you are able to use your long column, I would suggest to do so.
      This way
      > you will be able to get the "right" amount of separation in the
      column to
      > better separate the heads. But my suggestion would be is to have
      the ball
      > valve AFTER the column and its packing BEFORE the N/S head. This
      way when
      > you open your pot still valve, and close off the N/S head, all of
      the vapor
      > and fluid in your packed column would be able to return to the
      boiler and/or
      > escape through your pot still valve. Otherwise I would believe that
      you
      > would trap some good alcohol vapor in the packet column when you
      try to
      > switch over to your pot still.>>

      You bring up a good point here - and one I have had a couple of off
      group dicussions with others about.

      Basically, there is going to be some retention of vapour in the
      column around the time of switchover. If the valve is at the bottom
      of the column, obviously it is liable to be lost - either condensed
      in the column or taken off to the angels.

      However if the valve is at the top of the column, as you say, it
      cannot be lost - but I would query if it is actually usable, as it
      will remain in the column (??) to keep the pressure equal -
      therefore, some good ethanol vapour will still be in the column even
      after the tails are coming through the pot still section. Does
      anyone have any comments on this? Any idea what type of volume
      (condensed vapour volume - i.e. lost ethanol) we are talking about?

      The way I see around this is:
      1. After foreshot come through, the still gets turned off. This has
      to be done, so I can swap the water connections from the N/S head to
      the pot still jacket condenser.
      2. In this off time, I have to wait for the vapour temp in the head
      to decrease below 40 degrees or so, otherwise I will loose vapour -
      this takes around 10 minutes from experience.
      3. Once this time is up, I swap the condenser connections over.
      Then open the pot still valve(3/4"), and close the N/S column valve
      (2").
      4. Power then goes back on (at half power!)

      I think this minimises vapour losses - there probably will be a small
      amount in the column, but I think it will be negligable, especially
      considering I am talking about 25L - 50L runs. It also negates any
      possibility of pressure buildup in the boiler.

      What do you think?

      Matt
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